H7N9 is shorthand for the current avian flu virus infecting and often killing people in China, and it's gotten the attention of public health types worldwide, Rick and I discuss on PodMed this week.  A study in the New England Journal of Medicine chronicles what is known about the virus at the moment, while CDC recommendations and updates published this week highlight recommended treatment for H7N9 infection.  So what is known?

First of all, H7N9 is a truly novel influenza virus of avian origin.  While H7 viruses arising from birds have been seen in human infections previously, this is the first N9 subtype identified.  In contrast to previously isolated H7 viruses, which usually cause mild conjunctivitis or moderate respiratory symptoms, this isolate is quite virulent.  The NEJM article describes the clinical course for three patients infected as presenting with high fever and cough, rapidly progressing to a need for intubation (declined by one patient) and death.  As of 4/25/ 2013, China has reported a total of 82 confirmed cases of this type of influenza, with 77% of them having had some type of bird exposure, either to live birds or dead ones.  Live birds can shed quite a lot of the virus and spread it in their mucus or droppings, and unfortunately, in contrast to bird flu isolates seen in the past, the birds themselves don't appear sick when infected. Sickly appearance or not, China has begun culling efforts of its poultry to attempt to limit spread of H7N9.

So what about that hallmark of pathogenicity and pandemic potential, human to human spread? Clearly, the virus hasn't yet acquired this ability to any great degree as so far, infections seem to be limited.  However, the study does point out that in two cases in China, human to human transmission cannot be ruled out, and historical data demonstrate that influenza viruses can and do 'learn' to become more efficient in their person to person spread.

Now, what about treatment?  The good news is the virus continues to be susceptible to oseltamivir (Tamiflu) and zanamivir (Relenza), and the CDC guidelines recommend their use even outside of the 48 hour window since symptom onset usually observed.  Treatment should be initiated at the same time as testing. 

Vaccine candidates are being developed apace, with most manufacturers predicting six weeks or so before such a vaccine would be available.  As Rick points out in the podcast, that old public health standby, isolation of cases, is being employed in China, and will hopefully limit spread of the infection.  Our modern twist of air travel  may hamper those efforts, however, so once again, covering your nose and mouth when sneezing, washing your hands assiduously, especially in public places like airports, and seeking treatment if you suspect you may have the flu or may have been exposed remain prudent measures.

Other topics this week include the benefits of an education effort to reduce worm infections in Chinese schoolchildren and a report card on improving risk factors in those with diabetes, both also in NEJM, and a link between valproate taken during pregnancy and autism in offspring in JAMA.  Until next week, y'all live well.



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H7N9 | jhublogs
April 26, 2013 at 12:20 pm
Biological Hazard – China, Hong Kong Special Administrative Region, Hong Kong : human case of avian influenza A H7N9 verified | Family Survival Protocol - Microcosm News
January 15, 2014 at 2:35 am

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Stephen Knows Cancer May 17, 2013 at 2:52 am

The H7N9 seems like a potential threat that certainly needs to be dealt with as soon as possible. I was in college when the swine flu was making national news, and I would not like to see anything like that again. Glad to hear that China has begun to take some precautionary steps in order to prevent the spread of this virus.


Daniel May 9, 2013 at 1:46 am

Sounds like the virus H1N1. I’m happy to hear that it is susceptible to oseltamivir and zanamivir. Let’s hope that they could develop the vaccine as soon as possible to prevent this virus.


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